Today’s invention is a tandem bicycle capable I reckon of setting (unfaired) speed records.
The rear rider sits on an extension of the normal frame and uses an extra set of pedals which drive the rear wheel through an additional gearset.
The design benefits from about twice the power and much less than twice the resistance (rolling, air drag).
Any record attempts might require solid tyres.
Although I’ve shown the riders’ legs in-phase, if there were enough space, it might be worth experimenting with say 90 degrees out of phase, in order to smooth the power delivery.